Time-continuous analog filters are extensively employed in systems for analog processing of high-frequency signals. A typical application is data reading from bulk memories (known in the pertinent literature as "disk-drive applications"). In this application, the cutoff frequencies of the filters currently lie in the 50 to 100 MHZ range.
As is well known, integrated electronic filters for high-frequency applications are currently manufactured using mixed bipolar-complementary MOS (BiCMOS) technologies Manufacturing with BiCMOS technology has certain drawbacks which have led the market to favor approaches based on purely CMOS technology. In this case, the MOS transistors can be operated within their linear or saturation range. An optimum solution would be operation in the linear range, where the transconductance of the transistors would also be linear and for a wider range of signals. Unfortunately, tranconductance in the linear range is lower in value than in the saturation range, and the resulting device has, therefore, a higher power consumption.
There are also several known alternative approaches for making time-continuous filters with high linearity. However, all these approaches have a drawback in that they exhibit non-linear transconductance when the MOS transistors are operated in the saturation range.